ImageOptim is excellent for publishing images on the web (easily shrinks images “Saved for Web” in Photoshop). It's useful for making Mac and iPhone/iPad applications smaller (if you configure Xcode to allow better optimization).

ImageOptim removes EXIF meta­data, such as GPS position and camera's serial number, so that you can publish images without exposing private information (but there's an option to keep the meta­data if you need it).

How does it work?

When you drag'n'drop images into ImageOptim's window it will run several image optimization tools automatically and combine their results, ensuring that you always get the smallest file.

ImageOptim integrates well with macOS, so you can also drop files on ImageOptim's Dock icon, or use Services menu in Finder, or Markup menu on attached images in Apple Mail. ImageOptim can also be launched from command line or Sketch.

A special option for even smaller files

By default ImageOptim is very cautious and exactly preserves image quality, but if you allow it to change the quality — even only a little — it will be free to use much more aggressive optimizations that give the biggest results. You can configure lossy optimizations in ImageOptim's Preferences. ImageOptim can apply lossy compression not only to JPEG, but SVG, anim GIF and PNG as well!

In preferences uncheck PNGOUT and Zopfli. Without these tools optimiza­tion will run much quicker, but will be a bit less effective.

Will ImageOptim be in the App Store?

No, and please beware of knock-offs in the App Store! Apple's has been selling three already.

ImageOptim is given for free on terms that basically say “you can do what­ever you want except taking this freedom away from others”. Apple does not allow such permissive terms. Apple requires all App Store users to accept DRM (copy protection) and legal restrictions in the iTunes EULA.

You can get ImageOptim here, DRM-free. Its license allows you to share it, modify it, use it in any country in the world — even sell it — if you don't forbid anybody else from doing the same.